Arteries of the heart, and more specifically coronary arteries, may sometimes be occluded or narrowed by atherosclerotic plaques or other lesions. These afflictions are generally referred to as coronary heart disease or a stenosis, and result in inadequate blood flow to distal arteries and tissue. Heart bypass surgery may be a viable surgical procedure for certain patients suffering from coronary heart disease. However, attendant with traditional open surgery, significant patient trauma, discomfort, extensive recuperation times, and life threatening complications may occur due to the invasive nature of the surgery and the necessity for stoppage of the heart during such a surgery.
To address these concerns, efforts have been made to perform interventional cardiology procedures using minimally invasive techniques. In certain efforts, percutaneous transcatheter (or transluminal) delivery and implantation of interventional coronary devices are employed to solve the problems presented by traditional open surgery. Typically, a guide catheter is first inserted through an incision into a femoral (transfemoral), or radial (transradial) artery of a patient. Transradial access is increasingly accepted as a method offering lower post-operative bleeding complications and quicker recovery times for patients. However the smaller diameter of the radial artery requires a smaller diameter guide catheter. The smaller diameter guide catheter has less back support than a similarly configured femoral guide catheter. For example, the Seldinger technique may be utilized in either method for percutaneously introducing the guide catheter. In such methods, the guide catheter is advanced through the aorta and inserted into the opening of an ostium of a coronary artery. A guidewire, or other interventional coronary devices such as a catheter mounted stent and/or balloon catheter, may be introduced through the guide catheter and maneuvered/advanced through the vasculature and the stenosis of the diseased coronary artery. However, when attempting to pass through a difficult stenosis, or when conducting a radial intervention using a small diameter guide catheter, the guide catheter may not have adequate back support, and continued application of force to advance the interventional device though the stenosis may cause the distal end of the guide catheter to dislodge from the opening of the ostium of the coronary artery, resulting in potential damage to the surrounding tissue.
In order to prevent the guide catheter from dislodging, interventional cardiologists sometimes would deep seat the guide catheter into the coronary artery. The term “deep seat” or “deep seating” means that the guide catheter would be pushed farther downstream into the coronary artery. However, deep seating the guide catheter risks the guide catheter damaging the coronary artery wall (dissection or rupture), occluding the coronary artery, and interfering with blood flow to the coronary artery.
One attempt to provide additional back support to a guide catheter that has gained acceptance is the use of a guide extension catheter. The guide extension catheter is deployed within a lumen of the guide catheter and extends distally from the distal end of the guide catheter into the coronary artery. Their smaller size, as compared to the guide catheter, allows the guide extension catheter to be seated more deeply in the coronary artery with less potential damage. This provides additional back support to the guide catheter to aid in delivery of interventional coronary devices. In cases with a difficult stenosis or radial interventions, the use of the guide extension catheter reduces the risk of dislodging the guide catheter from the opening of the ostium of the coronary artery during treatment. However, with their smaller size, guide extension catheters may pose difficulty in receiving an interventional coronary device within the passageway of the distal shaft of the guide extension catheter. As an example, an interventional coronary device such as a catheter with a stent mounted on an outer surface of a balloon may catch, snag, or otherwise become snared on the entry port of the distal shaft of the guide extension catheter. While efforts have been made to ease the introduction of interventional coronary devices into the passageway of the distal shaft of the guide extension catheter by angling or skiving the entry port of the distal shaft, these methods are only in a single plane and have not eliminated the instances of catching and snagging of interventional coronary devices on the entry port of the distal shaft of guide extension catheters.
Accordingly, there exists a need for an improved guide extension catheter distal shaft entry port design that provides easier entry into the passageway of the distal shaft and reduces catching and snagging of interventional coronary devices advancing into the passageway of the distal shaft.